Patella dislocation is one of the most common pathologies of the knee joint. The medial patella femoral ligament plays a pivotal role in the avoidance of patella-femoral instability. Rupturing of the medial patella femoral ligament is the main pathological consequence of patellar dislocation. All acute dislocations cause some degree of macroscopic medial patella femoral ligament damage and studies have shown that lateral dislocation invariably results in at least some damage to the medial patella femoral ligament. About 44% of non-conservative treated patients go on to suffer re-dislocation along with painful symptoms and chronic instability.
Medial patella femoral ligament reconstruction surgeries prevent further dislocation of patella by adopting one of the surgical techniques selected from medial patella femoral ligament reconstruction with a divergent patellar trans 2-tunnel technique; Y graft (fixation of femur first); C graft fixation of patella first (2 incision, first 3 cm longitudinal incision is along the proximal medial border of the patella and another 1 cm above the medial patella femoral ligament insertion); V shaped tunnel in which tunnels are drilled 1.5 cm at the supero medial half of the patella with sufficient distance between the tunnels to avoid fracture; and a docking technique for medial patella femoral ligament reconstruction.
Applicant knows of no special intra-operative method of determining the anatomical location of the patella that can help in identifying the exact medial patella femoral ligament insertion site other than an intra-operative x-ray imaging. Unfortunately, such an x-ray based procedure is accompanied by a high risk of radiation exposure to the patient, the surgeon, any medical assistants as well as other technical staff. The medial patella femoral ligament is the main passive restraint against patella-femoral instability and lateral patellar displacement.
Non-anatomic reconstruction of the medial patella femoral ligament can lead to non-physiologic patella-femoral loads and kinematics. The double bundle technique effectively limits rotation and sliding throughout the range of movement thereby minimizing postoperative instability.
The medial patella femoral ligament may be defined as a thick band like condensation of soft tissues extending from the patella to the medial femur. The average width of patella insertion of medial patella femoral ligament is about 17 mm (a general range of 14 to 20 mm). Average width of the femoral origin on the medial epicondyle is 15.4 mm (a general range of 11 to 20 mm). Average patella height is about 44 mm (a general range of 40 to 47 mm); width is about 34 mm (a general range of 24 to 39 mm) and a thickness of about 22 mm (a general range of 18 to 27 mm).
The inventors perceive that there is scope for the provision of an accessory that obviates, at least to some extent, the need for the use of intra-operative x-rays.
The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.